1. Field of the Invention
The present invention relates to a ceramic container for a rechargeable battery and an electric double layer capacitor, and a battery and electric double layer capacitor using the same, and more particularly to a battery and an electric double layer capacitor which are used as a slim-type battery for a small-sized electronic apparatus such as a cellular phone, a backup power supply for a semiconductor memory, a spare power source for a small-sized electronic apparatus and the like, and a ceramic container used therefor.
2. Description of the Related Art
In recent years, the rapid development of portable apparatuses typified by a cellular phone, a mobile computer, a videotape recorder with an integrated camera and so on, has increased the need for reduced size and weight. At the same time, the demand for an increase in battery power has been increased research on size and weight reductions while increasing the energy density of the battery. In particular, since a lithium battery is a battery using lithium having a small atomic weight and a high ionization energy, in order to realize such a battery that a high energy density can be obtained and a size and a weight can be reduced, and furthermore, recharging can be carried out, research for lithium batteries has been increasing, and now, and lithium batteries have been used in various applications such as a power source for a portable apparatus.
Moreover, an electric double layer capacitor has such a structure that positive and negative charges are arranged opposite to each other at a very short distance over an interface where two different phases (for example, a solid electrode and an electrolyte) come in contact with each other, and is an electric element capable of charging and discharging an electrical energy by utilizing an adsorbing layer of an ion in the electrolyte formed on a surface of a carbon material such as graphite, boronated graphite, active carbon or coke for a positive electrode material and a negative electrode material, that is, an electrostatic adsorbing and desorbing action of an ion in an electric double layer formed on the surface of the carbon material such as graphite for the positive electrode material and the negative electrode material. An inner part of the electric double layer capacitor is constituted by a separator composed of a nonwoven fabric formed of a polyolefin fiber or a fine porous film formed of polyolefin, two polarizable electrodes each formed of a carbon material and disposed by interposing the separator therebetween, and the electrolyte, The electric double layer capacitor is classified into two types of an organic solution type and a solution type, depending on a difference in the electrolyte.
Thus, the electric double layer capacitor utilizes the storage of the electric charges in the electric double layer formed on the interface of the two polarizable electrodes and the electrolyte. Therefore, it is possible to store a very large electric charge corresponding to a surface area of the polarizable electrode until an electrolysis of the electrolyte is generated by exceeding a withstand voltage.
In an electric double layer capacitor using the organic solution type, particularly, a driving voltage can be set to be 2 to 4 times as high as that of an electric double layer capacitor of the solution type using a solution such as aqueous sulfuric acid in the electrolyte. An electrical energy E which can be stored is expressed in E=CV2/2, wherein a voltage is represented by V and a capacity is represented by C. Therefore, a high energy density can be obtained.
In recent years, there has been proposed a slim-type secondary battery and an electric double layer capacitor in which a battery element or an electric double layer capacitor element constituted by a positive electrode (or a first polarizable electrode), a negative electrode (or a second polarizable electrode) and a separator and an electrolyte shown in FIG. 8 are accommodated in a ceramic base.
The conventional secondary battery or electric double layer capacitor has a ceramic base 11, a lid 15, a positive electrode B-1 or a first polarizable electrode B-1, a negative electrode B-2 or a second polarizable electrode B-2, a separator B-3 and an electrolyte B-4 as shown in FIG. 8. The ceramic base 11 has a hollow or open portion formed by a side wall and a bottom portion. In the ceramic base 11, a first metallized layer 12a is formed on a bottom face facing the hollow or open portion of the bottom portion, and a second metallized layer 12b is formed on an upper surface of the side wall facing the hollow or open portion. Furthermore, the ceramic base 11 is formed of sintered alumina and so on. The lid 15 is formed of a metal such as an iron (Fe)—nickel (Ni)—cobalt (Co) alloy. A container is constituted basically by this ceramic base 11 and this lid 15. The secondary battery or the electric double layer capacitor has a sealing type structure in which an element including the positive electrode B-1 or the first polarizable electrode B-1, the negative electrode B-2 or the second polarizable electrode B-2 and the separator B-3 impregnated with the electrolyte B-4 which separator is interposed between the electrodes is disposed in this container and between the first metallized layer 12a and the lid 15. Charging and discharging in the metallized layer 12a and the lid 15 are carried out through first and second electrodes C and D formed on a lower surface of the ceramic base 11 (for example, see Japanese Unexamined Patent Publication JP-A 2004-227959 (Pages 4 to 6 and FIG. 1).
In a battery or an electric double layer capacitor using the ceramic base 11 shown in FIG. 8, ceramics is excellent in a chemical resistance. Therefore, the ceramic base 11 is hard to be damaged by the electrolyte B-4 containing an organic solvent or acid and an impurity dissolved from the ceramic base 11 can be prevented from being mixed into the electrolyte B-4 to deteriorate the electrolyte B-4. Thus, the good performance of the battery or the electric double layer capacitor can be maintained.
However, there is a problem in that the use of the electrolyte B-4 having a high performance causes a component of the first metallized layer 12a to be dissolved into the electrolyte B-4, thereby deteriorating the electrolyte B-4 and degrading the performance of the battery or the electric double layer capacitor, or the corrosion of the first metallized layer 12a causes an electrical conductivity of the first metallized layer 12a to be damaged, and furthermore, the first metallized layer 12a to be disconnected.